Internal combustion engine



Nov. 26, 1940. w BQXAN INTERNAL COMBUSTION ENGINE Filed Aug. 10, 1936 3 Sheets-Sheet l I'm/entanl I/ x 714 J M I Nov. 26, 1940. w. B OXAN 2.223,o90

INTERNAL COMBUSTION ENGINE Filed Aug. 10, 1936 3 Sheets-Sheet 2 I nventon- M30 Xi Nov. 26, 1940. w. BOXAN 2,223,090

INTERNAL COMBUSTION ENGINE Filed Aug. 10, 1936 3 Sheets-Sheet 3 Inventor":

Patented Nov. 26, 1940 UNITED STATES 2,223,090 INTERNAL COMBUSTION ENGINE Walter Boxan, Zschopau, Germany, assignor to Auto Union Aktiengesellschaft, Ohemnitz, Germany Application August 10, 1936,.Scrial No. 95,256

6 Claims.

This invention relates to an air-compressing internal combustion engine, more particularly a vehicle engine, with self-ignition, airless injection and a precombustion chamber which is in communication with the combustion chamber'through throttling openings.

It is known to inject the fuel directly into the combustion chamber (jet atomisation). In this case the fuel is taken up by a substantially quiescent (stagnant) mass of air, which reaches its self-ignition temperature without further losses of energy, that is already when starting or during idle running. Although-such engines start reliably, they suffer,owing to the combustion pressures acting directly on the power piston, from harsh running (Diesel knock) which makes them unsuitable for certain uses, more particularly as driving engines having a high speed of revolution i for motor vehicles. v a

20 It has also been proposed to inject the fuel only indirectly, that is into a precombustion chamber (ignition atomisation) In this case, there is im- .parted to that part of the air charge which is pushed over into the precombustion chamber an 25 additional motion, which assists the working up of the fuel in the precombustion chamber. In this case the fuel is taken up by an eddying (rotating) mass of air. Such engines run very smoothly, but the final compression temperature 30 required for self-ignition is reached only when the engine is running, that is, has become warmed up. When starting, however, in idle running the energy losses of the pushed-over part of the air are so great that the engine can only be kept in 35 operation by auxiliary means, for instance sparking plugs. Such additional arrangements are however very undesirable for reasons of construction,'operation and economy.

The object of the invention is to'unite the ad- 40 vantages of these two methods, whileavoiding their disadvantages, and this is effected through such an arrangement of the throttling openings between the precombustion chamber and the combustion chamber that a portion of the air charge 45 is pushed over in a substantially eddying state and' a second part in a substantially quiescent state into the precombustion chamber, the fuel Germany August 12, 1935 ignition and thereby initiates the combustion of that portion of the fuel which'is taken up by the eddying (rotating) air charge. Only the former, usually smaller portion of the air charge experiences a sudden increase in pressure, whereas the 5 latter, usually greater portion of the air charge experiences only a gradual increase in pressure. The initially great increase in pressure, which is in the region of the upper dead centre,

can thus not cause harsh running, as it is very 10 soon overtaken by the final, gradual pressure increase which comes in the region of the expansion stroke. The result is therefore actually obtained, that the ignition difliculties in starting and idle running are overcome without any further auxiliary means and that smooth running of the engine is ensured in all circumstances, even in the higher speeds of revolution.

The arrangement according to. the invention is illustrated in the drawings by three constructional examples:

Fig. 1 shows a vertical main section through the first precombustion chamber type,

Fig. 2 a section on line II--II of F 1,

Fig. 3 a section on line III-III of Fig. 2, 4

Fig. 4 a vertical main section through a second precombustion chamber type,

Fig. 5a section on line VV of Fig. 4,

Fig. 6 a section on line VIVI of Fig. 5,

Fig. '7 a main section through a'third precombustion chamber type, I

Fig, 8 a section on line VIIIVIII of Fig. 7 and Fig, 9 a section on line IX-IX of Fig. 8.

r In the first constructional example shown in Figs. 1 to 3 the precombustion chamber is connected by its cylindrical wall 3 with the bottom 4 of the cylinder cover. In the bottom 5 of the precombustion chamber 2 throttling openings are provided, which consist of a central passage 6 and four tangential passages 1. The tangential .pas- 40 sages] are arranged circumferentially around the central passage 6 and are of helical shape at the periphery of the precombustion chamber 2. The places 8 where the tangential passages 1 open into the precombustion chamber 2 and the places 9,-

. where the central passage 6 opens into the cylinder space 10 are well rounded off. In the cover wall ll of the precombustion chamber 2 the injection nozzle I2 is mounted coaxially with the. central passage 6, the nozzle cap l3 being at the top about flush with the chamber wall H. The fuel is injected in the form of four jets H which are distributed radially in the direction of the precombustion chamber wall -3, without coming in contact with the latter. v

version of pressure energy into velocity energy, in

the precombustion chamber 2, until it fills substantially-timezone A of the diameter ii. That portion of the charge which flows through the zone A. The combustion will then take place tangential passages I in the sense of the arrow b spreads out in an eddying fashion however, that is to say with an additional conversion of pressure energy into velocity energy, in the precom-' bustion chamber 2, the circular eddying being formed in the latter, which fills the zone B. The boundary given by the measurement (2 between the zones A, B depends of course on the ratio of the cross-sections of the passages 6, 'I. Preferably, the volume of the zone. B is greater than the volume of the zone A. Now, if the fuel be injected, as is usual, somewhat before the upper dead. centre, the jets M will first pierce the quiescent part of the air in the zone A and will be in part consumed therein, before they pass into the eddying part of the air of the zone B, where they will be entirely consumed.- Self-ignition of.

the mixture will then start in the zone A, as the quiescent glowing mass of air in-this zone first reaches the self-ignition temperature of the'fuel in all circumstances. This mass of air, when being pushed over, sufiers no heat losses, .partly owing to the small amount of throttling in the passage 6 and partly owing to ,its insulation in the eddying belt of the zone B. The fuel passing into the zone B is immediately churned up, that is mechanically worked up in a -thorough manner, but it only reaches its self-ignition temperature,- on being further compressed through the compression wave due to the precombustion in the suddenly with a great increase of pressure in the precombustion chamber 2', causingthe mixture to be blown out by way of the throttling openings 6, 1 into the combustion space l0; Through the rounding-off of the inlet places 8, 9 on either side it is possible to cause the throttling resistance oi the passage 6 to fall during the inflow and that l of the passages I during the outflow.

Owing to the increase of pressure in the precombustion chamber, the mixture will flow back into the combustion chamberduring the return flow by way of the passages 1 with circulai' movement and during the return flow by ways of the passage- 6 with radial movement. The air charge is thereby completely mixed with the'mixture and a complete main combustion is obtained.

In the constructional exampleshown in Figures 4 to 6, the bottom 5 of the precombustion chamber 2 is formed as an incandescent insertion, which isfflxed by-means of a thread I! directly in the wall 3. In this case sixtangential passages I are provided. The tangential passages terminate towards the precombustion chamber, side and the central passage? towards the combustion space side in ribs l8, l9. Thefuel is, injected in three jets I in the direction of the bottom 5 between the passages 6, 1' at such an inclination that that part of the precombustion chamber 2 which is above the jet cone (of the angle 0:) corresponds substantially to the eddying zone B and that portion'which is below the same to the quiescent zone A. The jets of m M thus'play half in eachaone n, B and are" consumed to an equal extent in the two. Below the'precombustion-chamber bottom 5 a cavity'20 I is preferablyv provided inthe cylinder end. 15.

- Nothing is'changed thereby as re g'ardsthe mode of operation or the v en'gineas compared with the first constructionalexample. The incandescent insertion whicnis the most heavily stressed part towards the combustion space I!) and reaches to the. bottomoutlet of the passage 6. Bythis means the'portlon of the'air resting in the pas-. sage 6, which presents the most'i avorable ignition conditions, canbe saturated with fuel; In the third constructional example,-Flgures '7 to 9, the bottom 5 ofthe precombusti'on' cha nber 2 ,{which is constructed as an incandescent it is also possible according to the invention to employ a further central injection jet "i, which is directed insertion is arched towards the injection nozzle l2. The eddying zoneB extends preirably between thewalls 5, H, whereas the quiescent zone A whicliis reduced to the diameteri-d extends through the centralcpassage s tothe cavity-fll of the piston. The fuel i'suinjected in the form 1 into .the zone B and in the form of a central'jet 0! three jets L4 arranged like the rays of a star;-

I6 into the zone A, so that ,each of these zones I receives an exactly-ap ortioned. quantity of fuel. Since the retardation offlignitioh in the the zone 'A between the preco'mbiistion chamber and pistonhead is less than in the'up'per part, the self-ignition of the fuel will 'beaccelerated' part of" even, if a smooth running of the engine .as in the I preceding constructional examples cannot be ob-.. tained owing to the first ignitionpressures'acting directly on thepi-ston head. I.

The arrangement 'according'to unites in aconstructionally simple'way two ac-,

tions which coincide as regards the time taken and therefore any 'coacting result both in a'continnouscombus'tion and in a continuous atomisatitan. The constructional means ior..'unltingthese methods can of, course: be still further? modified, without exceeding the scope or the, in-

.vention. Which method predominates depends on the requirements and can be controlled as desired, both by'a suitable distribution oi! the air over the precombustion chamber and the combustion space and by a suitable dimensioning ofthe zones A, B. The question ofthfe distribution goes handin-hand withjthe question-oi the fuel distribution through suitable jet 'formatiofi.- e

What I claim is: 5

1. Inan air compressing internal combustion engine with selij-lgnition .airless injection, a cyl- 'inder having a combustion chamber therein and a precombustion chamber having'a cylindrical side wall and a bottom separating said chambers,

said bottom having a'central axial passage and a plurality of side passages therein connecting cylinder.

' said chambers, said side passages being disposed 'helically or the cylinder axis and opening-into the preco mbustion chambertangentially of the cylindrical side wall, and means for injecting 2.- In an compressing intemalcombustion engine with self-ignition airless injection; 2. cylq 1 40' the invention inder having a combustion chamber therein and a precombustion chamber having a cylindrical side wall and a bottom separating said chambers, said bottom having a central axial passage and a plurality of side passages therein connecting said chambers, said side passages being disposed helically of the cylinder axis and opening into the precombustion chamber tangentially of the cylindrical side wall, and means for injecting fuel into the precombustion chamber, said fuel injecting means being constructed and arranged to inject a number of fuel jets correspondin to at least one-half of a total number of side passages, the axes of the jets being directed toward the ends of the'side passages opening into said precombustion chamber.

3. In an air compressing internal combustion engine with self-ignition airless injection, a cylinder having a combustion chamber therein and a precombustion chamber having a cylindrical side wall and a bottom separating said chambers, said bottom having a central axial passage and a plurality of side passages therein connecting said chambers, said side passages being disposed helically of the cylinder axis and opening into the precombustion chamber tangentially of the cylindrical side wall, and means for injecting fuel into the precombustion chamber, said fuel injecting means being constructed and arranged to inject a number of fuel jets corresponding to at least one-half of a total number of side passages, the axesof the jets being directed toward the ends of the side passages opening into said precombustion chamber, said injecting means also being constructed and arranged to inject a fuel jet toward said bottom and int the central passage. I

4. In an air compressing internal combustion engine with self-ignition airless injection, a cylinder having a combustion chamber therein and a precombustion chamber having a cylindrical side wall and a bottom separating said chambers, said bottom having a central axial passage and a plurality of side passages therein connectin said chambers, said side passages being disposed helically of the cylinder axis and opening into the precombustion chamber tangentially of the cylindrical side wall, and means for injecting fuel into the precombustion chamber, the ends of the sidepassages opening into the precombustion chamber being rounded and the end of the central passage adjacent the combustion chamber being also rounded.

5. An engine as claimed in claim 1, characterized by the provision of rib-like projections surrounding the ends of the side passages opening into the precombustion chamber and the end of the axial passage opening into the combustion chamber.

6. In an air compressing internal combustion engine with self-ignition airless injection, a cylinder having a combustion chamber therein and a precombustion chamber having a cylindrical side wall and a bottom separating said chambers, said bottom having a central axial passage and a plurality of side passages therein connecting said chambers, said side passages being disposed helically of the cylinder axis and opening into the precombustion chamber tangentially of the cylindrical side wall, and means for injecting fuel into the precombustion chamber, the bottom of the precombustion chamber being arched towards said injection means.

ALTER BOXAN. 

